1.) To determine if 18F-setoperone PET scanning will define a difference in 5HT2 receptor occupancy and display in patients with seasonal affective disorder when compared with normal, volunteers and whether the extent of the affective disorder will bear a quantatative relationship th these PET scan findings. 2.) To determine if patients responding clinically to therapy will manifest a normalization in their PET scan findings, and a significant change from their pre-therapy study.